He said: “It is just a matter of money to go into the future. If we had enough money we would build a starship, in principle it is not very hard.

“You go very fast away or you go near a black hole. You come back and you have travelled into the future.

“If you want to go into the next century, into the next millennium then it’s easy; you just get enough money, go near a black hole, wait a little bit, come back and you are as much as you want in the future.”

This is because of the way time works.

Dr Rovelli says: “Earth is a big rock and mass slows time.”

Albert Einstein first proposed the idea that travelling at the speed of light away from Earth would slow down time for the traveller, while those back on Earth would experience time at the normal rate.

While you are travelling at the speed of light, time stays slow relative to the people who are standing still back on Earth.

As a result, you would be going fast while your clocks back on Earth would still be going at the same rate.

It is also due to the fact that time passes differently at different heights, with it being slower the higher in Earth’s atmosphere you go.

Dr Rovelli quips: “Your head lives longer than your feet.

“Time is far more complicated than the way we usually think about it. We have a simple idea about time; time passes the same for everybody, clocks measure it, past is different from the future.

“But as soon as we study nature more in general – the universe at large, galaxies, black holes – we realise that time works very differently in our daily experience.”

As for travelling backwards in time, Dr Rovelli says that is unlikely.